The present invention relates to a novel kind of equipment of catalytic distillation technology in chemical industry and a new catalyst handling system for use therein. The present invention is especially useful for the production of methyl tertiary butyl ethers (MTBE) from methanol and isobutene contained in C.sub.4 stream.
It is well-known that a catalytic distillation column is an apparatus for carrying out distillation and chemical reaction simultaneously therein to drive an equilibrium -limited reaction to completion by removing at least one of the products by virtue of their difference in boiling point. Because the reaction heat is absorbed by liquid evaporation, it can be fully utilized. What is more, the reaction is carried out at constant temperature without additional heat exchanger.
In order to carry out reaction and separation concurrently, and to make possible upward vapor and downward liquid flow through the reaction section in the middle of the catalytic distillation column, many structures have been developed. U.S. Pat. No. 3,634,543 discloses a reaction process carried out in distillation column wherein catalyst is contained in the downcomers of distillation trays in the column as additional bed, so that the catalytic reaction takes place in the catalyst beds and the distillation takes place on the trays in the column. The problems which arise are that the catalyst in the downcomers may cause flooding and that the loading of the catalyst is rather complicated.
U.S. Pat. No. 4,439,350 discloses a structure for holding catalyst in perforated or porous metal or plastic containers, such as fine stainless steel baskets. The containers are placed on the conventional distillation tray so that the liquid reactants would flow in and through the containers, and the vapor would be easily released from the liquid. When flowing through the trays, the reactants diffuse into the catalyst bed and react there.
In addition, U.S. Pat. No. 4,215,011 discloses a catalyst handling system wherein the particulate catalyst is contained in an array of bags made of glass fiber cloth and enclosed in stainless steel mesh. These bags are placed in the reaction section of the column. Between the bags there is a space to permit vapor and liquid to go through this section countercurrently.
All kinds of catalyst holding structures described above have the disadvantage of being relatively complicated and expensive to manufacture and replace Also, it is difficult to load new catalyst or to withdraw the used catalyst.
To carry out these operations, the operator will have to work in the column. Finally, because catalyst is packed in bags the reactants will have to diffuse into the bags to react therein, while the products must diffuse out. Therefore, the very inefficient contact of reactants with catalyst results in too poor utilization to achieve the desired chemical conversion.